Considerable progress has been made in understanding how electrical signals are generated and used within the body. This progress has led to the ability to monitor various medical conditions by means of transferring electrical energy from the body of a patient. This transfer of electrical energy can be accomplished with electrode systems, which use electrodes to contact the skin of the patient and then transfer the electrical energy from the patient to a recording/monitoring device.
Examples of electrode systems include Computed Tomography imaging (“CT”) scans, cardioscopes, electrocardiographs, and electrocardiograms (“ECG”). Unless otherwise indicated, the term “ECG electrode system” will be used herein to represent all or any of these electrode-based devices. Such systems can be used for monitoring the operation of the heart, the respiratory system, and the arterial system.
Generally, a basic ECG electrode system includes the use of at least two electrodes and corresponding electrical lead wires. These lead wires transfer electrical energy from the electrodes, in position upon a patient, to a monitoring apparatus. The electrodes are typically small, round or square, electrically conductive patches, which can be attached to the patient's skin with an adhesive, or with suction, to make electrical contact with the patient's skin. Examples of such electrodes include the Holter Stress Monitoring adhesive electrode manufactured by Lead-Lok, Inc., and Chest Suction Electrodes manufactured by Medesign, Inc.
As is well known, chemical reactions within the body produce electrical current that can be monitored when the electrodes are placed on a patient's skin. Electrical signals generated by the patient's body are transferred from the patient through the electrodes to a monitoring apparatus via the lead wires. The monitoring apparatus then converts the electrical signals from the patient into graphic representations, which a clinician then interprets. Such monitoring apparatuses include the Microscan 2000 manufactured by Advanced Biosensor or the ELI 100/STM ST Monitor manufactured by Mortara.
Presently in the United States, a majority of the ECG electrode systems use some form of adhesive to adhere the electrode to the patient's skin. Examples of such systems include the ZIP TAB™ ECG monitoring electrodes manufactured by Taylor Industries, the Wet Gel/Clear Tape electrodes manufactured by Kendall, Inc, and the 1700 CLEARTRACE™ tape electrode manufactured by ConMed. While these adhesive ECG electrode systems can be useful in performing ECG monitoring, there are significant problems associated with them. First, such a system can result in considerable discomfort for the patient. Typically the area where the electrode is to be placed must first be shaven to ensure proper electrical connection. This process not only takes time, which adds to the expense of the overall procedure, but is also uncomfortable for the patient and increases the chance of injury and infection. Further, there are considerable costs associated with the use of these disposable electrodes, including the cost of the electrodes themselves, plus delivery costs, storage costs, and disposal costs.
Second, most adhesive ECG system electrodes are manufactured to be disposable, having some or most of their component parts in plastic form in order to permit the electrodes to be discarded after use, thereby resulting in additional waste and burden on the environment. Another drawback associated with conventional adhesive ECG systems is the loss of adhesiveness when the electrode is removed from the skin. For example, if a clinician needs to move an already adhered electrode in order to obtain a better patient signal, the chances of the electrode being effectively re-adhered to the patient are greatly reduced. This is because the electrode's ability to adhere is reduced each time the electrode is removed from the patient's skin. Yet another drawback is the risk that the patient might be allergic to the adhesive itself. Finally, there is the time consuming process of cleaning the adhesive off of the patient's skin after the ECG process is completed.
To address these problems, a handful of ECG electrode systems rely on suction, rather than adhesives, to attach the electrode to the patient's skin. The suction is created with a vacuum inside of the suction cups, which house the electrodes. In use, the electrodes can be effectively adhered to the patient's skin by placing the suction cup on the patient's skin. As the vacuum is created, the low pressure that results causes the patient's skin to rise up slightly toward, and into contact with, the electrode. Once attached in this fashion, the patient's electrical signals can travel from the electrode through a lead wire to a suitable monitoring station.
Early types of ECG suction electrode systems, such as that described in U.S. Pat. No. 2,580,628 and similarly manufactured by Medesign, Inc., employ an electrode in the form of small hemispheres made out of steel with a small rubber ball at the top end. Although quite simple in operation, such electrodes suffered from the inconsistent vacuum produced.
To resolve these drawbacks manufacturers began using pumps connected to the electrodes through air hoses to create the vacuum inside of the suction cup. Conventional pumps create the vacuum within an electrode by sucking air toward the pump, thereby creating negative pressure inside the suction cup. The negative pressure, in turn, pulls the cup toward the skin of the patient thus engaging the electrode with the skin. However, ECG electrode system must typically use low-suction vacuum pumps or reaction pumps, and thereby avoid the use of large suction, which could produce a high risk of a hematoma, leading to a variety of related problems. The use of low suction, however, increases the chance that electrodes will fall off in the course of use. This meant the ECG system operator would have to spend valuable time re-adhering the electrodes and this extra time produces extra labor costs.
In turn, ECG electrode systems such as those described in U.S. Pat. Nos. 3,640,270 and 4,556,065 began using more powerful pumps to reduce the amount of time it takes to secure the electrodes to the skin. However, such systems increased the risk that the vacuum might become too strong and thus increase the risk of hematomas. To prevent this from happening, the operator must manually adjust the pump to maintain the appropriate vacuum, in addition to also monitoring the ECG data itself.
Another disadvantage of the pump-based ECG systems, as described above, are the difficulties relating to the removal and re-adherence of the electrodes. For example, if an operator desires to move a single electrode after suction has been created, the operator must first turn off the pump; then wait for the suction to dissipate; move the electrode to its desired location; and finally reinitiate the suction process all over again. A further disadvantage, of both ECG pump systems described above, is that the air flowing towards the pump can carry contamination into the pump system, such as sweat, hair, and electrode paste. Although filters can be used, the risk of contamination of the system and infection of the patient is not entirely avoided. Further, the contamination of the pump system requires the system to be cleaned frequently and makes the cleanup of the system extremely difficult. The problems surrounding the cleanup of the system are also compounded by associated labor costs.
The above-described ECG electrode systems also tend to have drawbacks associated with their design. Because of their suction pump construction, the US Food and Drug Administration restricts the use of such systems in the United States due to the high possibility of cross-contamination. These systems are also limited due to their bulkiness. The fact that the systems must house pumps to generate the suction causes them to be quite heavy. Further, the acquisition modules or distribution boxes which route the signals to the recorders/monitors can be large and heavy due to the electronics on board which digitize the signals coming form the patient before being routed to the ECG recorder. This bulkiness causes the systems to be heavy and immobile and therefore reserved for use in one location. Finally, typical ECG system lead wires are 1/16 of an inch in diameter. These lead wires are expensive and reputed to break quite often due to their thin design and repeated movement throughout an ECG procedure.
What is clearly needed are ECG systems that provide an improved combination of various features, including physical characteristics (such as weight and compactness), cost, clinical efficacy, environmental protection, and patient comfort.